Officials didn’t say, however, how they’d concluded that Iran was responsible for the blast, which struck the bus as it was heading to a parking lot at the international airport at Burgas, Bulgaria, a popular destination for Israelis. No group claimed responsibility for the bombing.

Guy Metel, an Israeli interviewed by Israel’s Channel Two news, said he was part of a group that had arrived on a trip organized by a Bulgarian tour company.

“We had just come out of the airport, and me and my family were told to get on bus number three,” Metel said. “We had just done that when we heard a huge explosion and everything shook. One of the other buses was just this fiery burning shell and people were screaming.”

He said that after removing his children from the bus, he tried to return to the scene of the bombing.

“It took forever for the paramedics to arrive. We were waiting and waiting, and I was holding a woman’s head who was bleeding badly. I could hear others calling for help,” he said.

Officials in Bulgaria said that a suitcase filled with explosives had been placed on the bus and detonated remotely.

Israeli officials said they were sending experts to Bulgaria to examine the scene and assist Bulgarian authorities in their search for suspects.

Israeli Deputy Foreign Minister Danny Ayalon said his country’s intelligence services had no information anticipating the attack. But intelligence officials had said in January that they’d asked Bulgaria to increase security for Israeli tourist groups after a suspicious package was found aboard a bus that was taking Israelis from Turkey to Bulgaria.

Wednesday’s bombing coincided with the 18th anniversary of the bombing of a Jewish community center in Buenos Aires, Argentina, that killed 85 people. That attack, Argentina’s deadliest terrorist incident, also was blamed on Iran.

Earlier this year, Israeli officials announced that they’d prevented attacks on Israeli targets in Azerbaijan and India. Last month, intelligence officials said Israeli nationals in Georgia, Thailand and Cyprus had been targeted in recent months. In February, a bombing in New Delhi wounded an Israeli diplomat’s wife. A cache of explosives found in Bangkok was linked to a separate plot to target Israeli diplomats there.

“All signs point to Iran,” Netanyahu said Wednesday. “They are targeting Israel wherever they can.”

Tensions between Israel and Iran have risen in recent years as Israeli officials warn that they might take action against Iran’s alleged nuclear-weapons program. Iran has accused Israel of conducting a “campaign against Tehran” and of masterminding the assassinations of several nuclear scientists in Iran.

White House spokesman Jay Carney said Wednesday that the United States "condemns such attacks on innocent people, especially children, in the strongest possible terms."